Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM AND METHOD FOR PAYLOAD ENCODING AND DECODING
TECHNICAL FIELD
[0001] The present disclosure relates to systems and processes for protecting
encoded
data, and, more specifically, to protecting media data that includes coding
that provides media
and/or market research.
BACKGROUND INFORMATION
[0002] Techniques such as "watermarking" have been known in the art for
incorporating
information signals into media signals or executable code. Typical watermarks
may include
encoded indications of authorship, content, lineage, existence of copyright,
or the like.
Alternatively, other information may be incorporated into audio signals,
either concerning the
signal itself, or unrelated to it. The information may be incorporated in an
audio signal for
various purposes, such as identification or as an address or command, whether
or not related to
the signal itself.
[0003] There is considerable interest in encoding audio signals with
information to
produce encoded audio signals having substantially the same perceptible
characteristics as the
original unencoded audio signals. Recent successful techniques exploit the
psychoacoustic
masking effect of the human auditory system whereby certain sounds are humanly
imperceptible
when received along with other sounds.
[0004] One particularly successful utilization of the psychoacoustic masking
effect is
described in U.S. Pat. No. 5,450,490 and U.S. Pat. No. 5,764,763 (Jensen et
al.) in which
information is represented by a multiple-frequency code signal which is
incorporated into an
audio signal based upon the masking ability of the audio signal. Additional
examples include
U.S. Patent No. 6,871,180 (Neuhauser et al.) and U.S patent 6,845,360 (Jensen
et al.), where
numerous messages represented by multiple frequency code signals are
incorporated to produce
and encoded audio signal. The encoded audio signal is suitable for broadcast
transmission and
reception as well
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as for recording and reproduction. When received, the audio signal is then
processed to detect the
presence of the multiple-frequency code signal. Sometimes, only a portion of
the multiple-
frequency code signal, e.g., a number of single frequency code components,
inserted into the
original audio signal, is detected in the received audio signal. However, if a
sufficient quantity of
code components is detected, the information signal itself may be recovered.
[0005] While media data encoding and watermarking has been known in the art,
there
continues to be great interest in additionally protecting the media data from
"hackers" or
"pirates." One well-known technique for protecting data is encryption, which
transforms
information using a cipher algorithm to make it unreadable to anyone except
those possessing a
key. Another related technique for protecting data is referred to as
"obfuscation," where input
data is encoded before it is sent to a hash function or other encryption
scheme. One of the
advantages of obfuscation is that it helps to make brute force attacks
unfeasible, as it is difficult
to determine the correct cleartext for decryption. Examples of obfuscation
techniques may be
found in Collberg et al.,"A Taxonomy of Obfuscating Transformations,"
Technical Report,
Department of Computer Science, University of Auckland, No. 148 (Jul. 1997),
Collberg,
Thomborson, "Watermarking, Tamper-Proofing, and Obfuscation- Tools for
Software
Projection," University of Arizona Computer Science Technical Report,
(February 10, 200), and
Sosonkin et al.,"Obfitscation of Design Intent in Object- Oriented
Applications," Department of
Computer and Information Science, Polytechnic University (2003).
[0006] While the aforementioned techniques of encryption and obfuscation has
served to
protect data files themselves, there has been insufficient work in area of
protecting media
measurement data, as well as data encoded using psychoacoustic masking. Under
the systems
and methods described below, key components of numeric and/or pattern-based
algorithms may
be eliminated from software applications intended for untrusted computing
environments. The
disclosed configuration provides a high level of protection against reverse
engineering because
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the software does not contain the actual software code implementation of the
algorithm, but only the numeric results of the algorithm. Accordingly,
attempts at
reverse engineering the code would not yield the actual algorithm. This
technique can
be extended to include protection of higher-level functionality using a set of
stored
patterns, representing the required algorithm flow, executed by a generic
pattern
engine. Because the stored patterns are not part of the actual software code,
they can
not be disassembled. By using a generic pattern engine, reverse engineering
may be
frustrated further.
SUMMARY
[0007] For this application the following terms and definitions shall apply:
[0008] The term "data" as used herein means any indicia, signals, marks,
symbols, domains, symbol sets, representations, and any other physical form or
forms
representing information, whether permanent or temporary, whether visible,
audible,
acoustic, electric, magnetic, electromagnetic or otherwise manifested. The
term
"data" as used to represent predetermined information in one physical form
shall be
deemed to encompass any and all representations of the same predetermined
information in a different physical form or forms.
[0009] The terms "media data" and "media" as used herein mean data which
is widely accessible, whether over-the-air, or via cable, satellite, network,
internetwork (including the Internet), print, displayed, distributed on
storage media, or
by any other means or technique that is humanly perceptible, without regard to
the
form or content of such data, and including but not limited to audio, video,
text,
images, animations, databases, datasets, files, broadcasts, displays
(including but not
limited to video displays, posters and billboards), signs, signals, web pages
and
streaming media data.
[00010] The term "database" as used herein means an organized body
of related data, regardless of the manner in which the data or the organized
body
thereof is represented. For example, the organized body of related data may be
in the
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form of a table, a map, a grid, a packet, a datagram, a file, a document, a
list or in any
other form.
[00011] The terms "coupled", "coupled to", and "coupled with" as used
herein each mean a relationship between or among two or more devices,
apparatus,
files, circuits, elements, functions, operations, processes, programs, media,
components, networks, systems, subsystems, and/or means, constituting any one
or
more of (a) a connection, whether direct or through one or more other devices,
apparatus, files, circuits, elements, functions, operations, processes,
programs, media,
components, networks, systems, subsystems, or means, (b) a communications
relationship, whether direct or through one or more other devices, apparatus,
files,
circuits, elements, functions, operations, processes, programs, media,
components,
networks, systems, subsystems, or means, and/or (c) a functional relationship
in
which the operation of any one or more devices, apparatus, files, circuits,
elements,
functions, operations, processes, programs, media, components, networks,
systems,
subsystems, or means depends, in whole or in part, on the operation of any one
or
more others thereof.
[00012] The terms "communicate," "communicating" and
"communication" as used herein include both conveying data from a source to a
destination, and delivering data to a communications medium, system, channel,
device or link to be conveyed to a destination.
[00013] The term "processor" as used herein means processing devices,
apparatus, programs, circuits, components, systems and subsystems, whether
implemented in hardware, software or both, whether or not programmable and
regardless of the form of data processed, and whether or not programmable. The
term
"processor" as used herein includes, but is not limited to computers,
hardwired
circuits, signal modifying devices and systems, devices and machines for
controlling
systems, central processing units, programmable devices, state machines,
virtual
machines and combinations of any of the foregoing.
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[00014] The terms "storage" and "data storage" as used herein mean
data storage devices, apparatus, programs, circuits, components, systems,
subsystems
and storage media serving to retain data, whether on a temporary or permanent
basis,
and to provide such retained data.
[00015] In accordance with various exemplary embodiments, systems,
methods and apparatuses are disclosed for protecting media data encoding and
decoding. Preferably, a minimum set of information needed to encode a single
message for an encoded audio signal is loaded separately from the media data
into an
encoder. A media license file is generated to protect the encoded data, where
the
underlying information relevant to the media data may be hidden through
encryption
in order to foster security. The algorithm(s) for encoding may be provided
using a
shared library, combined with an encoding payload that provides the minimum
information set required to form the single message. The combination is then
encrypted and sent over a network to a remote encoder factory application that
instantiates encoding channels after unpacking the combination.
[00016] For decoding, a partial decoder may be utilized to apply
pattern
matching information in the encoded payload. The matching is preferably
performed
in a decoder algorithm in order to confirm that the encoding is actually
present and is
proper. Accordingly, the payload must be successfully decoded and verified
before
the underlying data may be decoded, due to the partial symbol/bin information.
[00017] Other objects, features, and advantages according to the
present
invention will become apparent from the following detailed description of
certain
advantageous embodiments when read in conjunction with the accompanying
drawings in which the same components are identified by the same reference
numerals.
BRIEF DESCRIPTION OF THE DRAWINGS
[00018] FIG. 1 is an exemplary block diagram illustrating a an
encoding
apparatus for generating a protected signal;
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[00019] FIG. 2 is a table illustrating an exemplary methodology
for
encoding information in an audio signal;
[00020] FIG. 3 is a system diagram illustrating components used
for
creating a protected signal;
[00021] FIG. 4 is a functional block diagram illustrating an
exemplary
decoding apparatus for decoding a protected signal; and
[00022] FIG. 5 is a functional block diagram illustrating the
installation
and execution of an encoding/decoding arrangement in an exemplary embodiment.
DETAILED DESCRIPTION
[00023] FIG. 1 is a functional block diagram of an exemplary
audio
.signal.encoder.10. Encoder 10 implements an optional symbol generation
function
12, a symbol sequence generation function 14, a symbol encoding function 16,
an
acoustic masking effect evaluation/adjustment function 18, an audio signal
inclusion
. function 20, and a license file / code processing function 21.
Preferably, encoder 10
comprises a software-controlled computer system. The computer may be provided
with an analog processor for sampling an analog audio signal to be encoded, or
may
input the audio signal directly in digital form, with or without resampling.
Alternatively, encoder 10 may comprise one or more discrete signal processing
components.
[00024] The symbol generation function 12, when employed,
translates
an information signal into a set of code symbols. This function may be carried
out
with the use of a memory device, such as a semiconductor EPROM of the computer
system, which is prestored with a table of code symbols suitable for indexing
with
respect to an information signal. An example of a table for translating an
information
signal into a code symbol for certain applications is shown in FIG. 2. The
table may
be stored on a hard drive or other suitable storage device of the computer
system. The
symbol generation function may also be carried out by one or more discrete
components, such as an EPROM and associated control devices, by a logic array,
by
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an application specific integrated circuit, or any other suitable device or
combination
of devices. The symbol generation function may also be implemented by one or
more
devices which also implement one or more of the remaining functions
illustrated in
FIG. 1.
[00025] The symbol sequence generating function 14 formats the
symbols produced by the symbol generating function (or input directly to the
encoder
10) into a redundant sequence of code or information symbols. As part of the
formatting process, in certain embodiments marker and/or synchronization
symbols
are added to the sequence of code symbols. Preferably, the generating function
14 is
implemented in a processing device, such as a microprocessor system, or by a
dedicated formatting device, such as an application specific integrated
circuit or a
logic array, by a plurality of components or a combination of the foregoing.
The
symbol sequence generating function may also be implemented by one or more
devices which also implement one or more of the remaining functions
illustrated in
FIG. 1.
[00026] As noted above, the symbol sequence generating function 14
is
optional. For example, the encoding process may be carried out such that the
information signal is translated directly into a predetermined symbol
sequence,
without implementing separate symbol generating and symbol sequence generating
functions.
[00027] Each symbol of the sequence of symbols thus produced is
preferably converted by the symbol encoding function 16 into a plurality of
single-
frequency code signals. In certain advantageous embodiments, the symbol
encoding
function is performed by means of a memory device of the computer system, such
as
a semiconductor EPROM, which is prestored with sets of single-frequency code
signals that correspond to each symbol. An example of a table of symbols and
corresponding sets of single-frequency code signals is shown in FIG. 4.
[00028] Alternatively, the sets of code signals may be stored on a
hard
drive or other suitable storage device of the computer system. The encoding
function
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may also be implemented by one or more discrete components, such as an EPROM
and
associated control devices, by a logic array, by an application specific
integrated circuit or any
other suitable device or combination of devices. The encoding function may
also be carried out
by one or more devices which also implement one or more of the remaining
functions illustrated
in FIG. 1.
[00029] In the alternative, the encoded sequence may be generated directly
from the
information signal, without implementing the separate functions 12, 14, and
16.
[00030] The acoustic masking effect evaluation/adjustment function 18
determines the
capacity of an input audio signal to mask single-frequency code signals
produced by the symbol
encoding function 16. Based upon a determination of the masking ability of the
audio signal, the
function 18 generates adjustment parameters to adjust the relative magnitudes
of the single-
frequency code signals so that such code signals will be rendered inaudible by
a human listener
when incorporated into the audio signal. Where the audio signal is determined
to have low
masking capacity, due to low signal amplitude or other signal characteristics,
the adjustment
parameters may reduce the magnitudes of certain code signals to extremely-low
levels or may
nullify such signals entirely. Conversely, where the audio signal is
determined to have a greater
masking capacity, such capacity may be utilized through the generation of
adjustment parameters
that increase the magnitudes of particular code signals. Code signals having
increased
magnitudes are generally more likely to be distinguishable from noise and thus
detectable by a
decoding device. Further details of certain advantageous embodiments of such
evaluation/adjustment function are set forth in U.S. Pat. No. 5,764,763 and
U.S. Pat. No.
5,450,490 to Jensen, et al., each entitled Apparatus and Methods for Including
Codes in Audio
Signals and Decoding.
[00031] In certain embodiments, the function 18 applies the adjustment
parameters to the
single-frequency code signals to produce adjusted single-frequency code
signals. The adjusted
code signals are included in the audio signal by the function 20.
Alternatively, the function 18
supplies the adjustment parameters along
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with the single-frequency code signals for adjustment and inclusion in the
audio
signal by the function 20. In still other embodiments, the function 18 is
combined
with one or more of the functions 12, 14, and 16 to produce magnitude-adjusted
single-frequency code signals directly.
[00032] In certain embodiments, the acoustic masking effect
evaluation/adjustment function 18 is implemented in a processing device, such
as a
microprocessor system which may also implement one or more of the additional
functions illustrated in FIG. 1. The function 18 may also be carried out by a
dedicated
device, such as an application specific integrated circuit or a logic array,
or by a
plurality of discrete components, or a combination of the foregoing.
[00033] The code inclusion function 20 combines the single-frequency
code components with the audio signal to produce an encoded audio signal. In a
straightforward implementation, the function 20 simply adds the single-
frequency
code signals directly to the audio signal. However, the function 20 may
overlay the
code signals upon the audio signal. Alternatively, modulator 20 may modify the
amplitudes of frequencies within the audio signal according to an input from
acoustic
masking effect evaluation function 18 to produce an encoded audio signal that
includes the adjusted code signals. Moreover, the code inclusion function may
be
carried out either in the time domain or in the frequency domain. The code
inclusion
function 20 may be implemented by means of an adding circuit, or by means of a
processor. This function may also be implemented by one or more devices
described
above which also implement one or more of the remaining functions illustrated
in
FIG. 1.
[00034] FIG. 2 illustrates an exemplary translation table for
converting
an information signal into a code symbol. As shown, an information signal may
comprise information regarding the content of, the characteristics of, or
other
considerations relating to a particular audio signal. For example, it is
contemplated
that an audio signal could be modified to include an inaudible indication that
copyright is claimed in the audio program. Correspondingly, a symbol, such as
SI,
may be utilized to indicate that copyright is claimed in the particular work.
Similarly,
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an author may be identified with a unique symbol S2 or a broadcasting station
identified with a unique symbol S3. Further, a.particular date could be
represented by
a symbol S4. Of course many other types of information could be included in an
information signal and translated into a symbol. For example, information such
as
addresses, commands, encryption keys, etc., may be encoded in such symbols.
Alternatively, sets or sequences of symbols, in addition to or instead of
individual
symbols, may be utilized to represent particular types of information. As
another
alternative, an entire symbolic language may be implemented to represent any
type of
information signal. Also, the encoded information need not be related to the
audio
signal.
[00035] Referring back to FIG. 1, one or more of the functions 12
through 20 may be implemented by a single device. In certain advantageous
embodiments, the functions 12,.14, 16 and 18 are implemented by a single
processor,..
and in still others a single processor carries out all of the functions
illustrated in FIG.
1. Moreover, two or more of the functions 12, 14, 16 and 18 may be implemented
by
means of a single table maintained in-an appropriate storage device.
[00036] The license file / code processing function 21 of FIG. 1
implements secure encoding of media streams in such a way to protect the media
stream and allow it to be integrated with third-party tools capable of
extracting and
restoring the data (e.g., audio from video format files). License file 21
(also referred
to as a "Media License File") serves in the exemplary embodiment as a
container for
encoding information in an encoded payload, where the encoded payload includes
only enough information to allow a pattern based encoder to generate one code.
[00037] Typically, the encoder 10 may be configured to allow the
resultant encoding to be verified as proper, or authorized for use. For audio
data, the
encoder 10 may have complete symbol/bin information embedded or hard-coded for
each layer. Preferably however, the encoder 10 may use pattern matching to
avoid
having complete symbol/bin information. In the case where partial symbol/bin
information is generated, the underlying audio data is better suited for
protection from
unauthorized users. Using the configurations detailed below, encoding may be
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subsequently verified as part of a file encoding service without having
complete
symbol/bin information.
[00038] Under one exemplary embodiment, a minimum set of
information needed to encode a single message for an encoded audio signal is
loaded
separately from the media data into the encoder 10. The message should
preferably
not be hard-coded into the source. When generating a Media License File 21,
the
underlying information relevant to the media data may be hidden through
encryption
in order to foster security, and to advantageously "future-proof' the encoding
algorithm against layer and message structure changes.
[00039] Referring to the exemplary embodiment, the encoding
algorithm may be provided using a shared library, combined with an encoding
payload that provides the minimum information set required to form the single
message. The combination is then encrypted and sent over a network to a remote
encoder factory application that instantiates encoding channels after
unpacking the
combination. The unpacking can be to a RAMDISK making it volatile. Under this
configuration, the encoding algorithms and payload do not have to reside
permanently
on the encoding machine, for improved security. Furthermore, the shared
library/payload configuration advantageously allows changes to the encoding
algorithm to be distributed to all potentially affected machines.
[00040] On the decoding side, a partial decoder is utilized to apply
pattern matching information in the encoded payload. The matching is
preferably
performed in a modified decoder algorithm (such as the one described in US
Patent
6,871,180, cited above) in order to confirm that the encoding is actually
present and is
proper. Accordingly, the payload must be successfully decoded and verified
before
the underlying data may be decoded, due to the partial symbol/bin information.
Additional details on the decoding may be found below in connection with FIG.
4
[00041] Turning now to FIG. 3, an exemplary media file encoding
system is disclosed. Primary components of the system include the encoding
engine
300, connection manager 301, and the security manager 301. Support components
of
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the system include integration interface 305, media/audio interface 307, and
transcoding interface 310. The media file encoding system illustrated in the
embodiment of FIG. 3 is particularly configured for transmitting/broadcasting
media
data, such as audio data, to multiple locations via connection manager 301,
where the
media data is encoded to allow authorized 3" parties to monitor audience data
exposure and/or usage. Accordingly, using the techniques disclosed herein, if
protected data fails to be authenticated via the encoded payload / Media
License File,
the interface components will simply transmit unencoded media/audio data. In
other
words, the system will appear to be functional to the audience, but the
unencoded
audio will not permit ri parties to monitor audience activities.
[00042] The connection manager 301 is primarily responsible for
interfacing with remote locations. Under an exemplary embodiment, connection
manager 301 may use network-based communications, sockets, or higher-level web
services. Typically, the connection manager 301 will wait for and accept
connections
from the interface components (305, 307, 310), where multiple simultaneous
connections are supported. It then handles the information flow between the
interface
and the encoding engine 300. The connection manager is configured to format
media/audio data stream for encoding, and also handle configuration and
control for
the encoding process. The connection manager 301 preferably runs in the system
background as an operating system (OS) service as a long-running executable
that
performs specific functions with or without user intervention. The service may
be
configured to start when the system is booted and run in the background as
long as the
OS is running, or can be started manually when required. As an example,
connection
manager 301 may be run as a WindowsTM service or a Linux daemon to performing
the disclosed functions.
[00043] The encoding engine 300 of FIG. 3 is configured in the
embodiment to provide encoding (e.g., digital watermark) to the input
media/audio
data. Encoding engine 300 receives packets of data from the connection manager
301, adds a digital watermark, and sends encoded packets back to the
connection
manager 301 (illustrated as bi-directional arrow in FIG. 3). The encoding
engine 300
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also generates encoding that is equivalent to hardware encoders (i.e. such as
that
provided in Arbitron's) Digital/SDI Encoders). The configuration and control
information, received from the external interfaces (305, 307, 310) and
validated by
the connection manager 301, is processed within the encoding engine 300. This
information includes, among other possible information, audio sample rate,
sample
size, packet size, and the encoded message definition. Thus, the encoding
engine 300
may operate as a thread or process, under the control of the connection
manager 301.
Multiple instances of the encoding engine 300 may be invoked by the connection
manager 301. The connection manager 301 should be configured to support both
local and remote hosting. Using network sockets, the encoding application can
run
locally on a client's computer or remotely on a workstation. For a fully
Internet
capable application, web service technology can be used to implement the
communications interface between the components
[00044] The security manager 302 communicates with the encoding
engine 300 and is responsible for ensuring that the use of the encoding engine
300 is
authorized. Security manager 302 may also be configured to support time-
limiting
use of the encoding engine. Furthermore, security manager 302 may also be
configured for activity logging. Each time the encoding application is
activated in
encoding engine 300, information about the session would be stored in an
activity log
303. The information logged would typically include date, time, operator, and
any
information about the media content that is available from the appropriate
interface.
In installations where an Internet connection to the target machine is
available, the
activity log could be remotely accessed.
[00045] Continuing with the illustration shown in FIG. 3, various
interfaces may be provided for communication with connection manager 301. One
such interface, integration interface 305, provides connectivity to 3rd party
application software 304 such that the encoding process can be integrated into
the
workflow of media/audio production houses to include such features as
transcoding
and non-linear editing systems. In a preferred embodiment, the integration
interface
305 would be additionally developed for each 3rd party application. As shown
in
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FIG. 3, the integration interface 305 is communicably coupled to 3"I party
application
304 and to connection manager 301. In the preferred embodiment, integration
interface 305 would be integrated and distributed together with the 3"I party
application 304 as a Windows DLL or Linux shared library, although other
arrangements are possible.
[00046] Media/audio interface 307 is preferably configured as an
application that operates between a media player 306 and output device 308.
Interface 307 is configured to intercept digital audio, at the point of
playback (e.g.,
home computer) and forward it to connection manager 301. The subsequently
encoded audio is then sent back the media/audio interface 307 and ultimately
to the
sound output device 308. Since the interface 307 intercepts the audio as it is
played
back, the format and contents of the media file does not become a factor. In
other
words, transcoding-and/or manipulation of the original file is not necessary,
and-the
only requirement is that a standard audio output device (as seen by the host
operating
system) be targeted by the client's media player application 306.
[00047] For applications where 3rd party transcoding software is cost
prohibitive and/or unavailable, a format-limited transcoding interface 310 may
be
provided for support. Supported media file formats include AVI, QuickTime, and
WAV, among others. In addition to the transcoding interface 310, a user
interface
application 309 is provided to control the overall process. During operation,
the
transcoding interface 310 would accept a media file in a supported format,
extract the
audio portion for encoding, and then integrate the encoded audio back into the
final
output file. To ease processing requirements, format conversion would not be
supported under a preferred embodiment. Thus, the interface would not be
required
to perform a generic transcoding application, but serve a secondary capability
leveraging technology that is incorporated as part of Sun Microsystem's Java
Media
Framework and/or Microsoft's DirectX.
[00048] Native code (e.g., C/C++) is preferably used to handle interface
components and signal processing elements that are computationally intensive.
Commercially available math libraries (e.g., Intel MKL) may be also used to
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support multi-threaded operation and is optimized for use on Intel processors.
Also,
in order to support the broadest range of host computers and application
areas, the
software should preferably be developed in Java. This would also allow use of
the
Java Media Framework (JMF) that provides cross-platform support for the audio
interface and the transcoding interface. However, because Java is a managed
language, that typically operates within a virtual machine environment,
additional
security measures will be required in this case.
[00049] Accordingly, the encoded Media License File 21 described in
connection with FIG. 1 and utilized in the system of FIG. 3 may serve to
protect the
underlying data. The license file is used to authorize use of the application,
and
contains an encryption key embedded in it to unlock the encoding engine and
the
Ethernet address of the target computer. The Ethernet address is used to
uniquely tie
the application to the target computer. Thus, the encoding application would
not
function unless the address of the machine matches that in the file. Under a
preferred
embodiment, the license file contains the numeric tables needed to generate
the
encoded message, rather than the message information itself. This provides two
levels of protection: (1) The dynamic message generation code, which contains
core
information, is not distributed as part of the application and (2) long
sequences of
floating-point numbers will not be of much use to hackers seeking to break
into the
code.
[00050] The message assignment for the license file may be static,
where a client receives one or more license files, and each file can be
applied to one
or more media files as needed. In order to support multiple license files, the
files
should be uniquely named, by preferably using the date and time of generation.
Also,
the license file should be tailored to a client's Ethernet address (physical
MAC
address) of the target machine. After one or more license files are is
generated, they
may be transmitted to remote client locations. Multiple instances of the
encoding
engine can be active on a single target machine, and each instance can encode
a
different media file, using the same or different license files.
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[00051] The message assignment for the license file may also use a
dynamic code assignment, where a client can receive a new license file and
message
for each encoding session. For dynamic coding, an active Internet connection
is
required between the client utilizing the encoding system. Client and session
information is sent to the operator of the encoding system, where the license
file is
created (typically on a server), and sent back to the client's application.
[00052] As mentioned above, the license file is encrypted to protect
its
contents. The encryption key should be a combination of a fixed key stored in
the
application and the target computer's Ethernet address (or other unique
information).
One method for protection against reverse engineering is the use of code
obfuscation
tools. Since the major components of the encoding application are to be
written in
Java, a Java byte-code obfiiscator can be used to render files that, when de-
compiled,
reveal little, if any, of the original program flow and_data structure. Code
obfuscation .
techniques include control-flow remapping, variable renaming and redundancy
(applying scope rules), and run-time string decryption.
[00053] Using control flow remapping, the logic and flow of the
program for the license file may be re-expressed, making the translation into
valid
source code difficult, if not impossible. This technique relies on the fact
developers
typically write software in a structured manner to make it "human readable"
and
organized in some a manner that makes it easy to maintain. However, such
constructs, while useful to developers, are of no use to a computer and the
liberal use
of jump instructions or obtuse instructions sequences makes no difference in
the final
execution of the code (akin to truly compiled languages like C or C++). But
such
measures do confuse de-compilers and result in de-compiled code that is much
harder
to understand.
[00054] Alternately, when using variable renaming, either alone or
combined with the other techniques, makes reverse engineering extremely
difficult.
Computer languages have scope rules, or rules about when a variable of a given
name
is active. As such, developers tend to use descriptive names for variables and
name
variables with different functions different names. While descriptive names
are useful
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to developers (and hackers), they are of no use to the computer. Thus,
variable
renaming exploits scope rules and creates many instances of variables (e.g.,
named
"a" or "b" etc.). When such code is de-compiled, it creates confusion as to
which
variable is being accessed and when, without a detailed understanding of the
scope
rules. In addition, it makes it difficult to discern the purpose of variables
because all
of the descriptive names have been removed.
[00055] As another alternative and/or addition, string
encryption/decryption may be used. Encryption and subsequent run-time
decryption
of textual information, or strings, can be important because string searches
are the
primary means by which hackers gain an understanding of the program flow.
Typically, strings contained in the binary program file can yield clues as to
the
whereabouts of key program functionality. For example, a hacker looking for
the
- code segments that deal with authorization can search for error
messages such as
"authorization failure" or "user not valid" in the program file. Since the
hacker
knows that the code segments dealing with authorization can, typically, be
found in
the vicinity of the error messages, his job has just been made easier.
Further, by
circumventing the program flow that leads to the error message being
generated, the
hacker can bypass the authorization process. If a hacker can't find any
intelligible
text messages, such attacks are significantly harder.
[00056] Other software options for protection against unauthorized use
may include tying the application software to a unique identification code
contained
within the target computer, such as the hard drive serial number. Hardware and
software combinations, such as security dongles, are a similar mechanism where
the
unique identification code is contained within the external dongle and the
dongle is
usually accessed using a cryptic instruction sequence. When application
software
reads the expected identification code from a license file or other protected
repository
(e.g., in cases where the unique ID is contained within the application
itself), the
software compares that code to the identification code of the computer.
Typically,
unique numbers such as. the hard drive serial number or the Ethernet
controller
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address are used. If the machine's identification code does not match the
expected
code, the application does not function.
[00057] In order to further improve the protection of encoded data,
one
or more portions of data related to the encoding may be omitted. One exemplary
encoding technique is Critical Band Encoding Technology (CBET), developed by
Arbitron, Inc. (for further information, see "Critical Band Encoding
Technology
Audio Encoding System From Arbitron," Technical Overview, January 2004
(Revision D), available at http://wvvvv.sbe15.com/literature/ Arbitron_CBET
Whitepaper.pdf ). Using the CBET example, certain portions of the CBET
algorithm
can be removed from the encoding engine component (see FIG. 3,300). In the
hardware encoders, the embedded software is configured to dynamically generate
the
numeric tables necessary to encode any given message. The hardware encoders
also
contain the complete frequency set for each defined layer (for prior encoding
detection as well as the need to handle any defined message). The precompiled
numeric tables, which would be contained in the license file, allows these
core
algorithms to be removed from the application software, leaving a hacker
without
useful information. Therefore, even in the event that the software is reverse
engineered or compromised, the extent of the damage would be limited.
[00058] Other elements of encoding data that may be protected under
the present disclosure includes:
[00059] Decoding Information: data defining the messages, symbols,
and code tone frequencies needed to perform the decode algorithm;
[00060] Message Codes: data including the combination of ID,
extension, and layer used to identify an encoding entity;
[00061] Decoding Algorithm: the process steps, using decoding
information, used to determine if an audio stream has message codes embedded
in it;
and
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[00062] .. Diagnostic Information: a compressed representation of
encoded material, spanning the layer set, used to validate the operation of
the
decoding shared library.
[00063] .. Turning to FIG. 4, the illustration shows a decoding process
under an exemplary embodiment. An audio signal which may be encoded, as
described hereinabove with a plurality of code symbols and license file, and
received
at an input 410. The received audio signal may be a broadcast, internet or
otherwise
communicated signal, or a reproduced signal. It may be a direct coupled or an
acoustically coupled signal. From the following description in connection with
the
accompanying drawings, it will be appreciated that the decoder 400 is capable
of
detecting codes in addition to those arranged in the formats disclosed
hereinabove.
[00064] Upon receipt, license file processing feature 401 serves to
process the security protocols described above. Under a preferred embodiment,
encryption/decryption keys are received at the decoding end prior to the
receipt of the
signal, where a volatile key is received using a secured link. The license
file
processing 401 then processes the license file (payload) to obtain access to
one or
more of decoding information, message codes, decoding algorithm and diagnostic
information. Once processed, the decoder 400 would have enough information to
decode the incoming signal.
[00065] .. For received audio signals in the time domain, the decoder 400
transforms such signals to the frequency domain by means of a function 402.
The
function 402 preferably is performed by a digital processor implementing a
fast
Fourier transform (FFT) although a direct cosine transform, a chirp transform
or a
Winograd transform algorithm (WFTA) may be employed in the alternative. Any
other time-to-frequency-domain transformation function providing the necessary
resolution may be employed in place of these. It will be appreciated that in
certain
implementations, the function 402 may also be carried out by analog or digital
filters,
by an application specific integrated circuit, or any other suitable device or
combination of devices. The function 402 may also be implemented by one or
more
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devices which also implement one or more of the remaining functions
illustrated in
FIG. 4.
[00066] The frequency domain-converted audio signals are processed in
a symbol values derivation function 403, to produce a stream of symbol values
for
each code symbol included in the received audio signal. The produced symbol
values
may represent, for example, signal energy, power, sound pressure level,
amplitude,
etc., measured instantaneously or over a period of time, on an absolute or
relative
scale, and may be expressed as a single value or as multiple values. Where the
symbols are encoded as groups of single frequency components each having a
predetermined frequency, the symbol values preferably represent either single
frequency component values or one or more values based on single frequency
component values.
[00067] The function 403 may be carried out by a digital processor,
such as a digital signal processor (DSP) which advantageously carries out some
or all
of the other functions of decoder 400. However, the function 403 may also be
carried
out by an application specific integrated circuit, or by any other suitable
device or
combination of devices, and may be implemented by apparatus apart from the
means
which implement the remaining functions of the decoder 400.
[00068] The stream of symbol values produced by the function 403 may
be accumulated over time in an appropriate storage device on a symbol-by-
symbol
basis, as indicated by the function 404. In particular, the function 404 is
advantageous for use in decoding encoded symbols which repeat periodically, by
periodically accumulating symbol values for the various possible symbols. For
example, if a given symbol is expected to recur every X seconds, the function
404
may serve to store a stream of symbol values for a period of nX seconds (n>1),
and
add to the stored values of one or more symbol value streams of nX seconds
duration,,
so that peak symbol values accumulate over time, improving the signal-to-noise
ratio
of the stored values.
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[00069] The function 404 may be carried out by a digital processor,
such as a DSP, which advantageously carries out some or all of the other
functions of
decoder 400. However, the function 404 may also be carried out using a memory
device separate from such a processor, or by an application specific
integrated circuit,
or by any other suitable device or combination of devices, and may be
implemented
by apparatus apart from the means which implements the remaining functions of
the
decoder 400.
[00070] The accumulated symbol values stored by the function 404 are
then examined by the function 405 to detect the presence of an encoded message
and
output the detected message at an output 420. The function 405 can be carried
out by
matching the stored accumulated values or a processed version of such values,
against
stored patterns, whether by correlation or by another pattern matching
technique.
However, the function 405 advantageously is carried out by examining peak
accumulated symbol values and their relative timing, to reconstruct their
encoded
message. This function may be carried out after the first stream of symbol
values has
been stored by the function 404 and/or after each subsequent stream has been
added
thereto, so that the message is detected once the signal-to-noise ratios of
the stored,
accumulated streams of symbol values reveal a valid message pattern.
[00071] FIG. 5 is an exemplary overview of the system decoding
operation under an embodiment directed to audience-measurement. The system as
illustrated in FIG. 5 comprises decoder panel 500, data server 503, interface
server
504 and format module 505. Interface server 504 serves as a centralized
processing
device for managing the data interface for the data server 503 and format
module 505.
Data server 503 (which may alternately be combined with interface server 504)
manages communications between decoder panel 500 and interface server 504.
Typically, data such as decode payloads and software upgrades would be sent to
data
server 503 from interface server 504. Data server 503 would produce data such
as
detection reports, panel status and new install updates. Format module 505
converts
information reported by the decoder panel 500, via data server 503, to a
format that
would be appropriate for respective applications, such as audience measurement
and
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the like. Typically, detection reports and queries linking user/device data to
detection
reports would be received at the format module.
[00072] Decoder panel 500 may be one or a collection of devices
having a decoder 501 and device application 502, where the panel 500 invokes
decoder 501, preferably using device application 502. Application 502 then
would
operate further to configure the decoder 501 to (1) operate on the media/audio
stream
using decrypted copies of the hash key and decoding information, (2) operate
on a
microphone input stream using decrypted copies of the hash key and decoding
information, (3) media/audio stream sample feeds, (4) periodically poll the
decoder
for detection of encoded (CBET) media/audio data, (5) report the encoded
(CBET)
detection data, along with user and device identification information, and
status
information to the data server 503, and/or (6) perform diagnostics on the
decoder.
[00073] As mentioned above, the decode payload associated with the
license file may include a hash key linked to an algorithm internal to the
decoder, and
may be used to unlock the decoder to permit operation. The decode payload also
may
include an encrypted decoding information byte array that defines the layers,
message
structures, and symbol durations for decoding. Furthermore, the decode payload
may
include an encrypted diagnostic data byte array that can be used as a source
for
verifying the decoding operation. These elements are preferably combined into
a file
package to be unpacked and incorporated into an encrypted rule set.
[00074] In an exemplary process flow overview of the operation of the
systems of FIG. 5 and FIG. 3, a panelist (i.e., the decoding end of the
system) would
receive and install the necessary application(s), along with a decoder (e.g.,
CBET),
under a software-based embodiment. The panelist's ID information and other
relevant information would be provided to data server 503, which in turn would
obtain Dynamic Code Package (DCP) information from interface server 504. The
DCP information may contain license information, decryption keys and
diagnostic
information that is incorporated in the DCP. If the DCP request is accepted by
interface server 504, the server generates a DCP that uses the panelist ID
information
(PDUID) as part of the encryption key generation, and further adds an
encrypted
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shared library, and send the DCP to the data server 503. The PDUID information
is
stored and linked to the key. The data server 503 parses the DCP, and license
information and key data are stored and linked to the PDUID. The encrypted
decoding information, encrypted shared library, encrypted Diagnostic
Information,
and decryption key are then sent to an installation routine executed on the
panelist
device.
[00075] The installation routine decrypts and installs the shared
library,
places the encrypted decoding information and encrypted diagnostic information
into
the encrypted rule store, and validates the operation of the shared library by
performing a diagnostic run. If the diagnostic run passes, normal operation is
started.
[00076] Continuing with the example, under normal operation, the
device application may request a decryption key from the data server 503 over
a
secure link using the PDUID when the panelist device needs to invoke the
shared
library. Data server 503 determines if the panelist device has a valid
license. If the
license is valid, the data server 503 sends the key to the panelist device
over a secure
link. The key is then used as input to the shared library during invocation
and then the
key is preferably deleted.
[00077] The shared library uses the input key to decrypt the
decoding
information, as well as diagnostic information (if used) as part of a set-up.
The shared
library is passed PCM audio data and operates on it to determine if encoding
(CBET)
detections are present. The device application periodically polls the shared
library for
detections. If the shared library has detections, it returns a linked list of
detection
structures that have as a field the IP sensitive message information encrypted
using
the input key. The device application adds information allowing the times of
detection
to be linked to GMT.
[00078] Enhanced detection information may be passed over a secure
link to the data server 503 by the device application 502, along with the
PDUID. The
data server 503 would then pass the enhanced detection information to the
interface
server 504 over a secure link along with the associated PDUID as part of a
periodic
=
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report. Interface server 504 could then validate that the enhanced detection
information is associated with a known PDUID. If so, the detection information
is
passed to a collection transformation module (not shown), which may be located
in
the format module 505.
[00079] Although various embodiments of the present invention have
been described with reference to a particular arrangement of parts, features
and the
like, these are not intended to exhaust all possible arrangements or features,
and
indeed many other embodiments, modifications and variations will be
ascertainable to
those of skill in the art.
